In this project the phenomena will be investigated which lead to functional recovery following spinal cord transection of lampreys. To lay foundation for this we will further characterize the locomotor central pattern generator (CPG) of the lamprey, since it is the CPG which must be successfully reconstructed to restore function. The physiology will include a comparison of oscillator stability between adult and larval cords, and an analysis of the role of the long tract coordinating fibers. Anatomical description of the tracts carrying coordinating fibers will be done to determine the pattern of distribution of the cells whose axons make up the tracts. Lampreys, larval and adult, will be spinal- transected. Their recovery will be further studied, and the behavior of the previously transected cords compared to controls. The regenerated neuronal processes will be mapped anatomically and compared to controls to determine whether the specific pattern of cell distribution correlates with functional recovery. Qualitative changes in segmental oscillators which result from spinal lesions will also be explored. A search for general principles of functional recovery which transcend the lamprey will be a major aim.